Saltatory Evolution of the Ectodermal Neural Cortex Gene Family at the Vertebrate Origin

• The ectodermal neural cortex (ENC) gene family, whose members are implicated in neurogenesis, is part of the kelch repeat superfamily. To date, ENC genes have been identified only in osteichthyans, although other kelch repeat-containing genes are prevalent throughout bilaterians. The lack of elaborate molecular phylogenetic analysis with exhaustive taxon sampling has obscured the possible link of the establishment of this gene family with vertebrate novelties. In this study, we identified ENC homologs in diverse vertebrates by means of databasemining and polymerase chain reaction screens. Our analysis revealed that the ENC3 ortholog was lost in the basal eutherian lineage through single-gene deletion and that the triplication between ENC1, -2, and -3 occurred early in vertebrate evolution. Including our original data on the catshark and the zebrafish, our comparison revealed high conservation of thepleiotropic expression pattern of ENC1 and shuffling of expression domains between ENC1, -2, and -3. Compared withmany other gene families including developmental key regulators, the ENC gene family is unique in that conventional molecular phylogenetic inference could identifynoobvious invertebrateortholog. This suggests a composite nature of the vertebrate-specificgene repertoire, consistingnot onlyofdenovogenes introducedat thevertebrateorigin but alsoof long-standinggenes withnoapparent invertebrateorthologs. Some of the latter, including the ENC gene family, may be too rapidly evolving to provide sufficient phylogenetic signals marking orthology to their invertebrate counterparts. Such gene families that experienced saltatory evolution likely remain to be explored and might also have contributed to phenotypic evolution of vertebrates.

Subject headings

NATURVETENSKAP  -- Biologi -- Evolutionsbiologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Evolutionary Biology (hsv//eng)

NATURVETENSKAP  -- Biologi -- Zoologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Zoology (hsv//eng)

Keyword

vertebrate novelty

saltation

gene loss

conserved synteny

whole genome duplication

Publication and Content Type

art (subject category)

ref (subject category)